1. Field of the Invention
The present invention relates to a vacuum vessel such as a process chamber or transport chamber which forms a vacuum processing apparatus which processes a liquid crystal display substrate, a semiconductor wafer, or the like, a vacuum processing apparatus comprising the vacuum vessel, and a vacuum vessel manufacturing method.
2. Description of the Related Art
Processes of forming a thin film on a liquid crystal display substrate, a semiconductor wafer, or the like and dry etching or heating are mainly performed in a vacuum. Alignment, transport, and the like required to process the substrate or wafer are also often performed in a vacuum continuously. To perform these processes, a vacuum processing apparatus is used in which a plurality of vacuum vessels are connected to each other through gate valves.
Liquid crystal display substrates are becoming larger and larger in recent years, and even a rectangular substrate having a peripheral portion with a side length exceeding 3 m has been introduced. To process such a large-size substrate in a vacuum, a large-size vacuum vessel is required. When a small vacuum vessel is required, a highly hermetic vacuum vessel can be manufactured by hollowing one metal block. When, however, a large-size vacuum vessel is required, a large metal block is difficult to obtain. Therefore, it is difficult to manufacture a large-size vacuum vessel using a method of manufacturing a small-size vacuum vessel.
As shown in FIG. 14, when forming a conventional large-size vacuum vessel, a plurality of metal plate members 101 and 102 are combined and bonded to each other by welding at welding portions 105 to form a frame-like constituent member, so that a mechanical strength is ensured (Japanese Patent Laid-Open No. 8-64542). When a pair of metal plate members 103 are attached to the frame-like constituent member, the air tightness of this large-size vacuum vessel is maintained. As the metal plate members, for example, aluminum or stainless steel plates are used, and their thicknesses may range approximately from 20 mm to as large as 60 mm. This is aimed at supporting the atmospheric pressure acting on the vacuum with the plate members, so the plate members will not deform largely.
When a vacuum vessel is manufactured by a method as in Japanese Patent Laid-Open No. 8-64542, the vacuum vessel becomes heavy. Since this method uses thick, large-size metal plate members, the metal stock as the material is expensive, and such plate members are difficult to obtain.
Problems arising from welding during the manufacture of the vacuum vessel include thermal strain. Hence, secondary cutting is necessary after welding. This increases the number of working steps. A comparatively bulky process machine is also necessary, leading to a high manufacturing cost and a long manufacturing time. In a manufacturing process employing welding, a working defect or the like is difficult to recover. Transportation of a large-size vacuum vessel formed by welding has limitations due to the allowable weight, width, and height of the transportation vehicle and legal restrictions. These limitations sometimes make transportation difficult.
Patent references 2, 3, and the like propose vacuum vessel manufacturing methods that do not use welding. In these manufacturing methods, the shape of a vacuum vessel is formed by combining comparatively thick metal plate members, and a seal member is arranged along the joining portion where the metal plate members are joined to each other.
Methods that do not use a comparatively thick metal plate member are proposed by Japanese Patent Laid-Open Nos. 5-103972, 5-326191, 6-29100, and 2008-21487. The method disclosed in Japanese Patent Laid-Open No. 5-103972 uses a plate member having a honeycomb structure in place of a comparatively thick metal plate member. Japanese Patent Laid-Open Nos. 5-326191, 6-29100, and 2008-21487 disclose a vacuum vessel using a comparatively thin metal plate member.
In the methods disclosed in Japanese Patent Laid-Open Nos. 9-209150 and 2007-299785 which manufacture a vacuum vessel without welding, the structure of the seal member becomes complicated. In Japanese Patent Laid-Open Nos. 9-209150 and 2007-299785, as the comparatively thick metal plates are used in combination, the vacuum vessel becomes heavy and the material cost of the metal plate member increases. It is difficult to obtain the material.
In Japanese Patent Laid-Open Nos. 5-103972, 5-326191, 6-29100, and 2008-21487, to form a closed space by bonding comparatively thin metal plate members, the metal plate members must be welded. Welding may cause thermal strain. Hence, secondary cutting is necessary. This increases the number of working steps. A bulky process machine is also necessary, leading to a high manufacturing cost. In the manufacturing method employing welding, a working defect or the like is difficult to recover. When transporting a large-size vacuum vessel formed by welding, limitations are imposed due to the allowable weight, width, and height of the transportation vehicle and legal restrictions. These limitations sometimes make transportation difficult.